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No Model.)

T. FINGER.

SCHOOL SLATE AND BLAG'KBOARD.

Patented July 22, 1884.

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Nrrnn STATES PATENT Fries.

THEODOR FINGER, OF GOBLENTZ, GERMANY, ASSIG-NOB TO SAMUEL BERNHEIM, OF NEW YORK, N. Y.

SCHOOL-SLATE ANDBLACKBOARD.

' SPECIFICATION forming part of Letters Patent No. 302,390, dated July 22, 1884. Application filed April 4, 1884. (No model.)

To all whom it may concern:

Be it known that I, THEoDoR FINGER, a citizen of the German Empire, residing at Coblentz, in the Empire of Germany, have invented certain new and useful Improvements in School-Slates and Blackboards, of which the following is a specification, reference being had therein to the accompanying drawings.

This invention relates to sch ool-slates,blackboards, and tablets having writing-surfaces of natural slate; and the object of the invention is to intimately and securely fasten a slate surface or plate to a backing or foundation board or plate of wood, papier-mach, metal, I 5 or other suitable material, whereby the slate surface will be rendered more strong and desirable than if made without such backing plate, and if fractured said slate surface will not loose its adherence to the backing-plate.

The invention will first be fully described, and then clearly indicated in the claims.

In'the accompanying drawings, Figure 1 is a face view of a double reversible slate in an open position. Fig. 2 shows a natural slate 2 surface and a backing-plate cemented thereto set into a surrounding frame. Fig. 3 exhibits a surface or plate of natural slate intimately secured to-a backing or foundation plate by an interposed layer of adhesive cement.

The letter A designates a backing-plate or foundation-board which is made of wood, papier-mach, metal, or other suitable material, and is of any required thickness. To this backing-plate is secured a plate or tablot of natural slate, B, in contradistinction to an artificial slate surface applied in a plastic state, the backing-plate and natural slate being intimately secured together at all points by means or" an interposed layer of adhesive cement, O. In practice, the layer or coating of cement is applied in a plastic or liquid state to the surfaces, either or both, to

be connected, and then proper pressure is applied by a hydraulic press or otherwise, for 5 causing a proper adhesion pf the two surfaces thus cemented together. Any approved adhesive cement is employed for uniting the backing-board to the plate of natural slate. After the interposed layer of cement has becomehard or dry the tablet or slate surface prepared in the above-described manner has its surface dressed or finished and the edges trimmed, so as to adapt it for use as an ordinary frameless writing-tablet, or the mounted slate surface is set into a border-frame, D; If greater strength or rigidity is required, the mounted slate surface or tablet A B C may be secured to a backing-board that is let into a borderframe. In the modification just described the grains of two wooden boards or plates may cross each other, so as to obtain a maximum degree of strength with boards of comparatively little thickness. Cement is used for securing the mounted slate surface to the back ing-board of the surrounding frame. In the case of blackboards, however, such a borderframe is generally not required.

It will be evident that I retain in my present invention a writing-surface of natural slate, which is unqualifiedly the most desirable and satisfactory surface that can be resorted to, and that I securely or intimately secure said natural slate surface to a backingboard or foundation-plate in such a manner that great strength and firmness are given to said slate surface, whereby under ordinary circumstances of use and transport the'breaking of the slate surface is prevented. If, however, the slate surface should be fractured, or any portion of its surface scale off, no portion thereof will loose its adhesion with the backing-board or foundation-plate, and thus the writing-surface is still continuous and in con dition for use.

I am' well aware that an artificial slate com position has heretofore been painted upon a backing board or plate, and that a writing surface of natural slate has heretofore been protected by a backing of wood or other material, as is evidencedin an application for patent heretofore filed by me.

I am aware that it is not new to make a school-slate of a plate of celluloid attached to a base-board by means of cement. 7

What I claim as new, and desire to secure by Letters Patent, is

l. A school-slate, blackboard, or writingtablet consisting of a foundation-plate or back ing-board, and a plate or surface of natural frame in which said backed slate surface is slate cemented at all points of its back surset, substantially as herein set forth. 1o face to said backingplate, substantially as In testimony whereof I affix my signature in herein set forth. presence of two witnesses.

5 2. Aschool-slate consisting of afoundation- THEODOR FINGER.

plate or backing-board, a surface or plate of \Vitnesses: natural slate cemented at all points of its back I-IERRMANN HoFFrmNN, surface to said backing-plate, and a border- WILHELM lownns. 

